fix signedness mess in rw_verify_area() on 64bit architectures

... and clean the unsigned-f_pos code, while we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 16 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index 5d431bacbea9..5520f8ad5504 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -30,18 +30,9 @@ const struct file_operations generic_ro_fops = {
 
 EXPORT_SYMBOL(generic_ro_fops);
 
-static int
-__negative_fpos_check(struct file *file, loff_t pos, size_t count)
+static inline int unsigned_offsets(struct file *file)
 {
-        /*
-         * pos or pos+count is negative here, check overflow.
-         * too big "count" will be caught in rw_verify_area().
-         */
-        if ((pos < 0) && (pos + count < pos))
-                return -EOVERFLOW;
-        if (file->f_mode & FMODE_UNSIGNED_OFFSET)
-                return 0;
-        return -EINVAL;
+        return file->f_mode & FMODE_UNSIGNED_OFFSET;
 }
 
 /**
@@ -75,7 +66,7 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
                 break;
         }
 
-        if (offset < 0 && __negative_fpos_check(file, offset, 0))
+        if (offset < 0 && !unsigned_offsets(file))
                 return -EINVAL;
         if (offset > inode->i_sb->s_maxbytes)
                 return -EINVAL;
@@ -152,7 +143,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
                         offset += file->f_pos;
         }
         retval = -EINVAL;
-        if (offset >= 0 || !__negative_fpos_check(file, offset, 0)) {
+        if (offset >= 0 || unsigned_offsets(file)) {
                 if (offset != file->f_pos) {
                         file->f_pos = offset;
                         file->f_version = 0;
@@ -252,9 +243,13 @@ int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count
         if (unlikely((ssize_t) count < 0))
                 return retval;
         pos = *ppos;
-        if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) {
-                retval = __negative_fpos_check(file, pos, count);
-                if (retval)
+        if (unlikely(pos < 0)) {
+                if (!unsigned_offsets(file))
+                        return retval;
+                if (count >= -pos) /* both values are in 0..LLONG_MAX */
+                        return -EOVERFLOW;
+        } else if (unlikely((loff_t) (pos + count) < 0)) {
+                if (!unsigned_offsets(file))
                         return retval;
         }